1. Field of the Invention
The invention relates to a device for insert a thin and flexible measurement probe into brain tissue.
2. Description of Related Art
Brain measuring probes are used in research and especially when intensively monitoring brain diseases or injuries, such as traumatic brain swelling associated with a skull fracture. Such measurements monitor the brain""s much-reduced oxygen supply in the presence of swelling in order to allow timely surgical and medicinal intervention.
Several parameters are required in such procedures, which mutually corroborate each other and which should be ascertained as simultaneously as possible or in rapid consecutive manner. Such parameters, for instance, are the pressure inside the tissue, the partial oxygen pressure (pO2), the blood flow determined by the laser doppler method, and fluorescence measurements by the NADH method of certain enzymes.
Thin and flexible brain measurement probes operating at a distal testing site are available to measure all the aforementioned parameters, and are designed to not harm the brain tissue even after being situated in the brain tissue for a substantially long time.
Appropriate devices to insert and affix the probes in the skull are already in use. They should be securely held against the skull and be tightly sealed in a sterile manner in their aperture to the brain. Such requirements are demanded especially because measurements frequently must be carried out over a period of days. The non-sterile environment and frequent patient motion must be taken into account.
A device of this kind is known from the German patent document 195 02 183 C1. The conventional skull screw used for such purposes secures strong affixation of the probes to the skull bone and sterile sealing of the skull borehole. On account of the compressive screw connection, the probe is sealed in highly sterile conditions in the screw""s longitudinal borehole. The protective sleeve assures tensile load relief for the usually exceedingly traction-sensitive probes and, hence, protects them against damage caused by patient movements. However, this known design incurs the drawback that the probes can only be used one at a time. Moreover, this design inherently is appropriate only for pO2 probes. Other parameters would have to be determined from separately-situated probes entailing additional skull drillings.
A more appropriate design of this kind is known from KATALOG 93/94 issued by GESELLSCHAFT FUER MEDIZINISCHE SONDENTECHNIK GMB, Dorfstrasse 2, D-24247 Kiel-Mielkendorf and from INTRACRANIAL INSERTION SYSTEM, IIS 3-way system. The skull screw disclosed therein comprises three mutually adjacent accesses to its longitudinal borehole. These accesses allow installing simultaneously the probes each with its own compressive screw connection. Accordingly three parameters may be determined simultaneously.
Unfortunately, this design requires laborious handling. Three compressive screw connections must be operated separately with ensuing heightened risk of leakage and hence loss of sterility at one of the connections. The screw being used requires special and expensive manufacture. Each probe requires separate traction relief. High costs are thus incurred by the hospital because of conventional single use of the probes. Also, there is a substantial drawback in that the probes enter the brain at different angles through the longitudinal borehole and, inside the brain, run in a mutually-diverging manner. If, in the event of operational error, the skull screw is rotated with its probes in place, the brain tissue shall be stirred with exceedingly disadvantageous consequences for the patient.
A design different from the above-discussed species is known from SCHAEDELBEFESTIGUNG [skull affixation] PF 190, drawing of Mar. 25, 1994, Perimed AB, Jxc3xa4rfxc3xa4lla, Sweden which was made public by distribution from the exhibition stand of GMS GESELLSCHAFT FUER MEDIZINISCHE SONDENTECHNIK MBH at the 45th annual exhibition of the German Society of Neurosurgery at Nuremberg, 19 through May 25, 1994.
The above known insertion device consists of a resilient stopper fitted with several boreholes to pass probes. The stopper is inserted into the skull borehole and can be compressed in the longitudinal direction using a screwdriver. As a result the skull borehole as well as the probes passing through the stopper are sealed.
However, this design entails the drawback first of the unreliable, resilient support against the skull bone. Furthermore both the sealing between the stopper and the skull borehole as well as the sealing of the probes inside the stopper are highly unreliable.
This design, therefore, can be put in place only by means of a cumbersome and extensive operation whereby, following insertion, the stopper and its outward directed lines run subcutaneously.
This known design offers the advantage of allowing simultaneous emplacement of several probes while suffering from the drawback of being impractical for routine use in a neuro-surgical intensive care facility.
An objective of the present invention is to create a device of the above species which is more economical, simpler and installed in more reliable manner.
In this design of the invention, several probes can be installed through several lumina of the same guide hose. This feature offers economy. A conventional, simple skull bone screw with one compressive screw connection is required. The guide hose at the same is a traction relief means for the probes and furthermore renders the manufacture more economical. The skull bone screw being used assures reliable fastening at the skull bone and good sealing and sterility of the skull borehole. By means of the known compressive screw connection, the probes are sealed in highly sterile manner inside the guide hose. Accordingly excellent sterility is assured. Since the compressive screw connection requires only driving a screw, installation and handling are simplified by the invention. Lastly, this invention offers the advantage that the probes run parallel in the lumina of the guide hose and into the brain tissue. In case of accidental rotation of the skull screw or of the protective tube, therefore, there will be only slight tissue damage in the brain. On the whole, the design of the invention is substantially more economical, simpler and more reliable than the known designs.
In further accordance with the present invention, the highly pressure-sensitive probes are protected by the protective sleeve in the area where they cross the very hard meninx.
All probe connections may be situated in mutually juxtaposed manner at the proximal, external end of the protective sleeve. However, in further accordance with the present invention, the probe connections can be implemented at the ends of the branched tubes individually and without being hampered by the other connections. Using flexible branched tubes, the probe evacuation means can be configured into different directions to corresponding hook-up elements.
In accordance with other features, the invention provides the advantagexe2x80x94relative to the equally applicable design of a separate sealing ringxe2x80x94of greater economy and easier handling because the sealing ring need not be handled separately. Moreover. the invention provides defined length adjustment of the protective sleeve.
In accordance with other features of the invention, because the applicable materials are few on account of tissue compatibility, sterilization properties and the like concerning the guide hose, the plastically deforming sealing ring tends to flow deformation due to the compression. This compression can be maintained long-term by a resilient element such as a rubber ring.
Provided there are correspondingly standardized length adjustments for the individual probes, these probes can be configured in very simple manner at the desired depths of insertion without the complexity of adjustment. When designing the guide hose in the manner of claim 3, the branch tubes for instance can be made into appropriate lengths.
As already cited above, the material selection of the guide hose is restricted by the various requirements for the tube. Appropriate materials are mostly low in resiliency. When compressing the guide hose in order to reliably seal in this manner the probes in the compression zone, the guide hose material must be compressed within the compression zone. This requirement is met also with respect to the other requirements on suitable materials. However, problems arise when dissolving the compressed connection if, in the case of insufficient restoring force, the guide hose no longer detaches off the probes and these probes then cannot be pulled. In such an event the entire guide hose together with all probes must be removed and inserted again. The present invention is designed to minimize or eliminate these problems. The guide hose in the zone of compressed sealing is made of another material of high resiliency and, in particular, offers a high restoring force. In this way reliable compressed sealing of the probes is assured under all circumstances and following disengagement of the compressed connection the probes shall be detached completely and therefore can be easily exchanged individually. The remaining elements of the guide hosexe2x80x94namely its two segments, one proximally and one distally from the compressible partxe2x80x94may be better matched during material selection to the desired requirements regardless of their resiliencies, that is for instance relative to tissue compatibility, good sterilization, tensile strength etc.
The compressible part also may be compressed externally in known manner using a resilient compression ring. Advantageously, however, and in accordance with the present invention, the compressive screw connection axially compresses the flange and in this manner mechanically upsets the compressible part in the axial direction, as a result of which it implements the required probes"" radial, compressive sealing. Consequently, a very simple and reliable design has been attained.
The compressible part may be connected, for instance by bonding or welding or suitable mechanical interlocking, at the adjoining ends of the proximal and distal ends of the guide hose into one assembled unit. However, such connections can be implemented on plastics only with difficulty and in particular tissue compatibility most of the time precludes bonding by adhesives. In this respect, further features of the invention are advantageous. By a fully separate design of the compressible part, the problems are circumvented and construction is simplified.
A guide hose fitted with a wholly separate compressible part can be installed only with difficulty in the device of the invention because the guide hosexe2x80x94which consists of a distal segment, a proximal segment and the compressible partxe2x80x94would have to be held by three hands during assembly. In this respect, the present invention is advantageous and provides an easily handled assembly unit of all three segments of the guide hose wherein the securing pin, for instance, is a mandril or guide wire installed in the one of the lumina, or also a special securing pin situated only between the ends of the proximal and distal segments of the guide hose that adjoin the compressible part.